1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device, and more particularly to an improvement for implementing an enhancement in a noise eliminating characteristic of a wiring compatibly with promotion of microfabrication and simplification of a manufacturing process.
2. Description of the Background Art
FIGS. 31 and 32 are sectional views showing a wiring structure for a high frequency used in a conventional semiconductor device which has been described in the document (Y. Odate, T. Usami, K. Otsuka, T. Suga, “A measurement and simulation study of transmission lines on micro-strip and stacked-pair structure for high speed signals,” Proc. Electronic Components & technology Conference, pp. 526-529, May 2000.), illustrating a micro-strip line and a stacked pair line which are provided over a semiconductor substrate, respectively. In the micro-strip line, a grounding conductor 203 is formed under a transmission line 201. Consequently, an electromagnetic field is collected into the grounding conductor 203. For this reason, a characteristic for eliminating the influence of a noise between the transmission line 201 and another transmission line 202 (that is, a noise eliminating characteristic) can be enhanced.
However, there has been a problem in that the noise eliminating characteristic is deteriorated if the transmission line 202 excessively approaches the transmission line 201, and therefore instead, a stacked pair line structure has been proposed. In the stacked pair line structure, the transmission line 201 and a grounding conductor 204 which have widths and thicknesses equal to each other are provided to make a pair so that an electromagnetic field is caused to converge. Consequently, the noise eliminating characteristic can be enhanced.
Also in the stacked pair line, however, there has been a problem in that the noise eliminating characteristic cannot be sufficiently obtained between the transmission line 201 and another transmission line arranged at the side thereof. In order to solve such a problem, a coaxial shield wiring structure has been proposed. FIG. 33 is a sectional view showing a coaxial shield wiring structure disclosed in Japanese Patent Application Laid-Open No. 6-216343 (1994). In the coaxial shield wiring structure, grounding conductors 211, 212, 213 and 214 are provided through an insulating film 215 vertically and horizontally with respect to a transmission line 210.
In the coaxial shield wiring structure, however, the grounding conductors 213 and 214 are provided on the left and right of the transmission line 210. In addition, these wirings are formed through transfer using a mask pattern. Therefore, the degree of integration is the same as that of an element formed according to a design rule which is twice as much as a currently used design rule (a design rule means a threshold value of a lithography resolution). Thus, there has been a problem in that microfabrication is inhibited. According to a wiring rule with microfabrication of 0.1 μm or less, furthermore, there has been a problem in that the noise eliminating characteristic is deteriorated between transmission lines arranged at the sides thereof. In addition, it is necessary to form a special contact hole in order to electrically connect the grounding conductors 211, 212, 213 and 214 to a semiconductor substrate. Therefore, there has been a problem in that a process for manufacturing a semiconductor device is complicated.